Cathode ray tube envelope construction



1955 H. P. BARASCH CATHODE RAY TUBE ENVELOPE CONSTRUCTION 2 Sheets-Sheet 1 Filed Oct. 25, 1952 INVENTOR- him 5 P/z/J BA RASCH Nov. 8 1955 H. P. BARASCH CATHODE RAY TUBE ENVELOPE CONSTRUCTION 2 Sheets-Sheet 2 Filed 001:. 25, 1952 [VI/ENTQR: #4 N5 Pws BAP/156W United States Patent Qfiice 2,723,044 Patented Nov. 8, 1955 CATHODE RAY TUBE ENVELOPE CONSTRUCTION Hans Pius Barasch, Beverly Hills, Calif.

Application October 25, 1952, Serial No. 316,8'2i) 10 19 Claims. (Cl. 220-23) This invention relates to cathode ray tubes and methods of fabricating the same, with particular reference to cathode ray tubes in which a sheet metal shell and a glass wall member form adjacent portions of the tube envelope.

This application is a continuation-in-part of my copending application Serial No. 168,201 entitled Cathode Ray Tubes, filed June 15, 1950, and later abandoned.

This invention is directed specifically to the problem of interconnecting the sheet metal shell and wall member. The problem presents certain difiiculties arising from the fact that the metal of such a shell has a different coefficient of thermal expansion than the glass wall member, which difference in rates of expansion in conjunction with the annealing conditions can introduce stresses in the seals, leading to leakages and cracks. Particularly in low grade chrome-iron alloys, irregularities in contraction 30 rates by phase changes in the crystallization and excessive deviations from other causes can occur, which irregularities and deviations are aggravated by the fact that the metal rim of the shell into which the glass is sealed is of considerable thickness, and is thereby more likely to exer- 35 else excessive shearing forces and stresses in the seal in the course of contraction. To keep such tolerances of mismatch of thermal expansion and contraction within permissible limits becomes even more difficult in cathode ray tubes of relatively large sizes, and is even more at) troublesome in the construction of non-circular cathode ray tubes having more or less rectangular screens.

One of the main reasons for the necessity of such close mismatch limitations arises from the fact that the atmosphere pressing on the glass face plate causes the face plate to exert severe pressure on the metal shell. In the usual cathode ray tube construction this pressure is transmitted through the sealing structure at the joint between the face plate and shell and therefore the sealing structure must not only accommodate relative movement between the face plate and shell arising from their different coefiicients of thermal expansion but also relative movement arising from this pressure transmittal.

It is one of the purposes of this invention to separate the sealing and compression functions referred to above, as a result of which closer matches between the sealing components can be employed, thereby relieving excessive stresses in the seal proper.

Other difficulties are encountered where the glass member is the face plate of the cathode ray tube and is provided with screen means either in the form of an inner coating or in the form of an inner auxiliary screen member, which screen means or member, is highly vulnerable to damage by heat. Such vulnerability must be considered in the application of heat for bonding parts to seal the juncture between the metal shell and the glass, especially 5 in the fabrication of cathode ray tubes for color television or in tubes with after acceleration screens.

The broad object of the invention is to meet the various described difficulties and to solve the problem of structurally interrelating the metal shell and the adjacent glass member in a vacuum-tight manner, with special reference to relatively large and non-circular cathode ray tubes. One of the specific objects of the invention, therefore, is to provide a vacuum-tight joint construction for metal and glass members that will permit independent strain free relative expansion of the two materials at the joint. Another specific object is to provide a joint construction and fabrication procedure that will eliminate the necessity for heating the junction between glass member and metal shell to any damaging extent in completing the final joint between the glass member and the metal shell. Another specific object is to provide a joint construction that permits independent relative movement between the metal and glass at the joint and a still further object is to provide such a joint inwhich, on the one hand, the face plate reinforces the shell against collapse and on the other hand, the shell reinforces the face plate against collapse. Broadly described these objects are attained by a joint construction in which the larger end or rim of the metal shell is in pressure contact with an annular face of the glass member, there being discontinuity of bond across the joint to permit relative movement between the two opposed surfaces. Independent sealing means, preferably flexible, is provided in a region apart from the opposed surfaces to interconnect the metal and glass in a vacuum-tight manner without interfering with the relative movement. An important advantage of such a construction is that the metal shell may be made of mild steel that is both inexpensive and easy to work.

Physical continuity across the glass-metal juncture must be provided in some manner to make the structure vacuum-tight but this invention permits the use of relatively thin material to form the seal separate and apart from the heavy structure that is subject to high magnitude compression forces. The relatively thin material, as compared with the thick material, readily accommodates stresses arising from differences in coefficients of thermal expansion and other causes, the thin material accommodating such stresses without rupture, separation or deterioration.

Where the glass member is the large end plate or face plate of the cathode ray tube, the connection between the flexible sealing means and the glass is made prior to the coating of the face plate or prior to the mounting of any auxiliary color screen on the inner side of the face plate and later in the final assembly of the cathode ray tube a second joint is made between the sealing member and the metal shell. in this procedure, exposure of the finished face plate and shell rim to heat is minimized in various ways. in thefirst place, heatto bond the flexible sealing means to the glass is applied before the face plate is prepared and before it is finally mounted on the shell.

In the second place, the flexible sealing means provides extensive sheet material between the prepared face plate and the zone where the second joint is madebetween the sealing means and the sheet metal shell, the arrangement thus providing a relatively long conduction path for heat flow from the second juncture to the vulnerable face plate sealing joint with ample opportunity for heat dissipation along the path. In the third place, the final assembly sealing juncture may be completed by means requiring relatively low heat application. Thus the final juncture may be provided by thin sheet metal flanges or by the use of solder having an appropriate melting point,

A feature of certain practices of the invention is that a portion of the sealing means serves as a metal facing for the glass member, normal to the tube axis, against which facing the rim of the metal shell presses in a slideble' manner. Thus the sealing means not only serves its primary sealing function but also provides a smooth sliding surface for the rim of the metal shell and protects the adjacent glass from the friction involved.

A further object in several practices of the inventionis to: minimize straininthe region where the flexible sealing means is bonded to the glass member. Straintends to rise because the flexible sealing means interconnects relatively movable parts and is itself subject to thermal expansion and contraction. A feature of the invention in this respect is the use of a sealing means in the form of a thin metal sealing sleeve that is of broken longitudinal cross-sectional configuration to cause the sleeve to flex rather than to stretch in response to longitudinal stresses. For this purpose the material of the thin metal sealing sleeve may be bowed, looped, corrugated or otherwise offset.

The scaling sleeve may be made of such a material as to match the respective non-linear glass expansion of the face plate or the neck part of the tube; As known to the art, special chrome ironand nickel" iron cobalt alloys can thus be combined with selected soft and hard glasses. Any suitable combination of metal alloy and glass may be within the scope of the invention. On the other hand, a non-matching combination of sealing sleeve material and face plate material may be used. For example, pure copper in combination with any kind of glass can be-used.

With reference to strengthening the sheet metal shell and with reference to reinforcement of the faceplate against collapse under external pressure, a feature of the invention is the formation of an annular shoulder on the glass face plate to be embraced by the metal rim of the shell for the purpose, on the one hand, of reinforcing the shell, and on the other hand, of reinforcing the face plate. The reinforcement of the face plate by the shell against collapse under atmospheric pressure may be understood when it is considered that the face plate is slightly arched or domed outward and therefore tends to respond to atmospheric pressure by radially outward pressure against the rim of the metal shell. A further feature in certain practices of the invention is a fabrication procedure that results in the rim of the metal shell embracing the shoulder of the glass face plate under at least sufficient tension to eliminate looseness of fit and to favor rigidity in the joint structure.

A special object of the invention is to lower the cost of aluminizing the face plate; The usual operation for applying the aluminum backing involves the evacuation of the completed envelope of the tube, each tube being separately treated. The present invention makes it pos sible to aluminize a number of the face plates in a batch, in one operation, in an evacuated chamber prior to incorporation of the face plates into the tube envelopes.

Another special object of. the invention is to provide a construction and assembly procedure which will permit a color screen or color screen assembly such as used in color television to be incorporated in the TV tube construction in a simple and economical manner without danger of damage. A color screen assembly is a delicate structure that is highly vulnerable to distortion by heat and it must be installed prior to the final bonding operation. The present invention solves this problem by reduc- 111g the amount of heat required for the final bonding oper tion and by provid ng a construction which places the final application of heat at a safe distance from the delicate color screen.

A further object is to provide a television tube having a shell shaped to receive a color screen assembly of substantially the same area as the face plate. Since the usual shell is conical and diminishes in cross-sectional area with distance from the face plate and since a color screen assembly has substantial thickness, the conical shell will not receive a full sized color screen assembly. The present invention provides a shell having a cylindrical or nearly cylindrical portion of uniform cross-sectional area ad acent the face plate, the axial dimension of. this portion being sufiicient to accommodate the thickness of a full sized color screen assembly.

The above and other objects and advantages of the invention may be understood from the following description of various embodiments of the invention together with. the accompanying drawings.

In the drawings, which are to be regarded as merel illustrative Fig. l is a longitudinal sectional view of a cathode ray tube incorporating one practice of the invention;

Fig. 2 is a fragmentary enlargement of portions of Fig. 1;

Fig. 3 is a fragmentary sectional view illustrating an intermediate stage in the fabrication of the joint between the metal shell and the face plate;.

Fig. 4 is a similar view illustrating an intermediate stage in the fabrication of the joint between the. metal shell and the glass neck;

Fig. 5 is a fragmentary sectional view indicating preferred dimensional relationships in the joint between the metal shell and the face plate;

Figs. 6 and 7 are fragmentary longitudinal sections showing two other embodiments of the invention for sealing the juncture between a metal shell and a glass wall member;

Fig. 8 is a similar view indicating preferred dimensional. relationships in the joint construction of the embodiment in Fig. 7; and

Figs. 9, 10- and 11 are similar views illustrating still further embodiments of the invention.

Fig. 1 shows by way of' example a cathode ray tube, the envelope of which is formed by a neck member 10, a sheet metal shell 11, and an end plate or face plate 12. The neck member 10 is'made of glass, for example, soda or lead glass, and is formed with a flared portion 13 which matches the smaller end of the sheet metal shell 11.

The sheet metal shell. 11 may be a simple cone but in the construction shown is formed with a conical portion 15 and a cylindrical portion 16 at the wide end of the conical portion, these two portions meeting along the line of juncture 1 7. If the cathode ray tube is of the non-circular type, the portion 15 of the sheet metal shell l ll will be somewhat pyramidal rather than conical and the adjacent portion 16 will be somewhat rectangular rather than truly cylindrical. The face plate 12, which may be made of soda-lime glass, conforms to the shape of the portion 16 of the sheet metal shell 11.

In accord with the teachings of the invention the construction shown in- Figs. 1 and 2 incorporates a sealing means for interconnecting the shell 11 and the face plate 12 in a vacuum-tight manner and a second similar sealing means for interconnecting the shell and the neck member 10 in the same manner. Both of these sealing means may be regarded as thin sheet metal sleeves. In this instance both sleeves are madev of multiple sheet metal parts but may be one-piece members. in the case of multiple parts, theindividual parts may be made of alloys of varying expansion coeificients.

in general the concept underlying. the method of joining the shell 11 and the face plate 12' is to provide a thin sheet metal sealing sleeve having one circumferential portion adapted for bonding tothe glass face plate 1-2 and another circumferential portion adapted for bondingto the metal shell 11 with a substantial extent of the thin metal sealing material lying between these two circumferential portions to provide a relatively long path for heat conduction and to provide ample opportunity for heat dissipation along that path. By virtue of such an arrangement a bond may be made between one cir cumf'erential portion of the sealing sleeve and the face plate 12, and later a second bond may be. made between a second peripheral portion of the thin metal sealing sleeve, and the sheet metal shell 1'1 at suflicient distance from the face plate 12 and. with sufiicient opportunity for heat dissipation to avoid undue heating of the first bond.

In the construction. shown, the sealing, means includes a thin metal ring 25 suitable for bonding directly to the glass. of the face plate 12 and a thin metal cylindrical member or sealing sleeve proper 26 which is united with the ring in a'gas-tight manner by welding or solder as indicated at 27. While both the ring 25 and the sealing sleeve 26 may be made of the same metal, there is usually good reason for using two different metals with the metal for the ring 25 selected especially for the purpose of uniting in a satisfactory manner with the glass of the end plate 12.

The ring 25 may be made of an alloy having substantially the same coeflicient of thermal expansion as the glass material of the face plate 12, which alloy, for example, may be a selected chrome-nickel alloy or a. chrome-iron alloy. The material of the ring 25 need not, however, have substantially the same coeflicient of thermal expansion as the glass if the ring material is sufficiently soft and pliable to yield to the expansion and contraction of the glass. Thus, the ring 25 may be made of pure soft phosphorous-free copper which will form an effective bond with the glass and yet will yield sufficiently to prevent damaging strains when the glass expands or con-- tracts under changing temperature. The sealing sleeve 26, being out of contact with the glass, may, of course, have a widely different coeliicient of thermal expansion and therefore may be made of inexpensive sheet metal such as mild steel.

The sealing sleeve 26 may be bonded to the shell 11 in any suitable manner at a circumference of the shell amply spaced from the glass face plate 12. The sealing sleeve 26 may be bonded directly to the sheet metal shell 11, but in the particular construction shown in Figs. 1 and 2 the sealing sleeve is bonded to a sheet metal ring 28 which is, in turn, directly bonded to the sheet metal shell. In the particular construction shown, the ring 28 is soldered or welded to the conical portion 15 of the shell 11 as indicated at 29 and an outwardly extending flange 30 of the ring is joined face-to-face with a similar mating flange 31 of the sealing sleeve 26, the two flanges being united in an air-tight manner by welding or solder as indicated at 32. Preferably the two flanges 30 and 31 are bonded together in a region sp'aced outward from the base portions of the two flanges to leave the two base portions free to flex away from each other thereby to provide a desirable yielding action.

It is apparent that when the cathode ray tube is evacuated, the external atmospheric pressure will cause the shell 11 and the face plate 12 to exert substantial pressure against each other. It is important to note that the rim of the shell 11 is not connected directly to any adjacent structure and abuts against an annular face in a slidable manner so that the rim is free to expand and contract radially without setting up destructive strains in the face plate 12. While such an annular face for sliding contact with the rim of the shell 11 may be provided by the glass material of the face plate 12, preferably the annular face is provided by a radialportion of the sealing means, the radial portion in this instance being provided by the ring member 25 of the sealing means. Preferably the ring member 25 is formed with a flange 37 on the outer circumference of the radial portion 36 and is formed with an inwardly turned flange 38 on the inner circumference of the radial portion.

In the preferred practices of the invention wherein the rim of the metal shell compressively embraces the annular shoulder of the face plate, the sliding action at the face plate joint is not a matter of simple bodily movement of the shell rim relative to the face plate. Actually the relative movement that is involved in the sliding action is radial creepage of the metal rim relative to the glass in response to temperature changes, the magnitude of the creepage increasing progressively from the inner edge of the rim to the outer edge. If the metal and glass were directly bonded togetherythe tendency for such relative movement to occur in response to temperature changes would destroy the joint. I

- The second sealing means at the juncture of the shell 11 with the neck member 10 may consist of a sealing sleeve 39 and a sheet metal ring 40 as shown. The sealing sleeve 39 is made of a material suitable for forming a permanent bond with the glass of the neck member 10 and may therefore be either an alloy having substantially the same coefficient of thermal expansion as the neck member or may be made of a thin metal that has a different coefficient of thermal expansion but is sufliciently soft and pliable to yield to expansion and contraction of the glass to which it is bonded. The sealing sleeve 39 is bonded to an annular face 41 on the end of the neck member 10 to provide an annular metal 1 face d2 for sliding contact by the adjacent edge or rim of the metal shell 11. Preferably the rim of the shell 11 is bent to form an inwardly turned flange 43 that rests flat against the annular metal face 42. The sealing sleeve 39 is of the configuration shown that permits it to extend between the shell and the neck member and also to extend outside the shell for some distance from the neck member.

The sealing sleeve 35 is bonded to the cooperating sheet metal ring 4'33 which is, in turn, bonded directly to the shell 11, for example, by soldering or welding as indicated at47. In the construction shown the sealing sleeve 39 is formed with an inner curved flange 48 and an outer flange 49, and the outer flange 49 is bonded face to face to a mating flange 50 of the ring 40, the bonding being accomplished by solder or welding as indicated at Here again preferably the base portions of the two mating flanges 49 and 56 are free to flex apart to provide a desirable yielding action.

The described construction permits the following highly advantageous fabrication procedure. First, the ring 25 with the sealing sleeve 26 united thereto is placed on the rim of the metal shell 11 with the rim turned upright to hold the ring substantially horizontal. If desired, a suitable cylindrical jig may be substituted for the shell 11 for this step in the fabrication procedure. The glass blank for the face plate 12 is then placed on the ring 25 in the manner indicated in Fig. 3 and then numerous flames are applied around the circumferential edge of the glass blank and also around the circumference of the ring 25 with consequent heating of the edge portion of the glass blank to molten state. The weight of the blank 12 together with gravitational force acting on the hot plastic portions of the blank cause the glass to flow into the configuration shown in Fig. 2 with the glass in intimate bond with the ring 25. After the glass plate 12 cools, it is removed from the shell together with the sealing sleeve and may be coated in the usual manner on its inner surface and may be provided with an auxiliary metal backing in a well known manner.

The next step is to bond the glass neck member 10 to the sealing sleeve 39 in the same general manner. Here again the metal shell 11 may be employed, or a similar jig may be used. Fig. 4 shows how the shell 11 may be turned with the flange d3 uppermost to support the sleeve 39. The glass blank 10 for the neck member is positioned as shown in Fig. 4 and heat is applied to cause the edge portion of the glass blank to become plastic and for gravitation to cause the glass to flow to the configuration shown in Fig. 2 with the glass in intimate bond with the sleeve member 39.

The next step is to attach the sheet metal ring 28 to the shell 11 in a position to mate with the sealing sleeve 26 and to attach the ring member 40 to the shell in a position to mate with the sealing sleeve 39.

In the final assembly of the cathode ray tube the finished face plate 12, with the ring 25 bonded thereto and with the sealing sleeve 26 bonded to the ring 25, is placed on the rim of the shell 11 and the two flanges 30 and 31 are bonded together. Then the neck member 10 with the ring 39 bonded thereto is placed on the other end of the shell 11 and the two mating flanges 49 and 50 are bonded together. Preferably the shell 11 is provided with one or more vent ports 52 in the region of the sealing'sleeve 2'6 and one or more vent ports 53' in the region of the sealing sleeve 39 for the withdrawal of air from the region of each sealing sleeve in the subsequent operation of evacuating the cathode ray tube.

It will be noted that in this fabrication procedure the ring 25 serves as a mold for the heated plastic glass of the face plate 12 to control the flow of the plastic material. The inner flange 38 of the ring not only serves as a guard to keep the plastic glass from reaching the surface reserved for the sliding action of the shell but also facilitates the formation of a shoulder 58 in the. glass face plate 12,. which shoulder reinforces the flange 38 from the inside. In like manner the sealing sleeve 39 controls the flow of the heated plastic glass at the end of the neck member 10' and the inner curved flange 48 of the sealing sleeve prevents the heated glass from flowing into the region reserved for the sliding action of the rim flange 43 of the shell 11. Substantial application of' heat may be necessary to attach the two rings 28 and 40 to the shell 11 because the Wall of the shell is relatively thick, especially in large size cathode ray tubes, but such heat application is carried out while the shell is separate from the face plate 12 and the neck 10.

The application of heat for the final bonding of the mating flanges 30 and 31 and the mating flanges 49 and 50 is relatively mild because only relatively thin mating members are involved. Moreover, the two mating flanges 49 and 50 may be bonded together while the shell 11 is still remote from the face plate 12. It is apparent that the relatively small amount of heat required to bond the two flanges 3t) and 31 together will not heat the metalto-glass bond at the face plate 12 to any significant extent because such heat must travel over a relatively long path of conduction through the material of the sealing sleeve 26 to reach the face plate 12 and heat is dissipated rapidly over. this long path.

If a color screen assembly that is highly vulnerable to damage by heat is to be installed in the television tube, the installation of the color screen assembly may be delayed until all of the described heat bonding steps are carried out except the final step of bonding the two flanges 30 and 31 together. With the color screen assembly installed, the final bonding of flanges 30 and 31 together may be carried out without any possible damage to the color screen assembly because, in the first place, only a mild application of heat is required to complete the final bonding step and, in the second place, the construction provides a relatively long path of heat conduction' from the region of the final bond to the region of the color screen assembly with ample opportunity for heat dissipation along the path of conduction.

An important advantage afforded by the invention in this respect is that the color screen assembly may be of maximum area. In prior art procedures, the final bonding operation that is carried out after the color screen assembly is installed comprises the welding together of relatively heavy shell flanges relatively close to the color screen assembly with consequent excessive radiation of heat. inward toward the color screen assembly. Under such conditions, a color screen assembly of maximum area would be seriously damaged for a considerable depth around its margin. To avoid this damage, color screen assemblies of reduced cross-sectional area have been employed to provide ample space between the outer zone of heat application and the peripheral edge of. the color screen assembly. In contrast the present invention permits the use of a color screen assembly of maximum area, the area being substantially that of the face plate.

Various provisions may be made to prevent the two sealing sleevesv 26 and 39 from creating excessive stress in the regions. where the sleeve members are bonded to.

glass. For example thetwo sealing sleeves may be made of soft pliable material such as phosphorous-free copper which will stretch so readily as to minimize stresses. Preferably, however, the sealing sleeves are so designed as to flex instead of stretch in response to' longitudinal forces created in the sealing sleeves caused by longitudinal expansion of the shell 11. Such provision for yielding by flexure may reside solely in the yielding joints provided by the mating flanges 30 and 31 and by the mating flanges 49 and 50. Alternatively, the desired flexing action may be provided by bowing, corrugating or otherwise offsetting the sealing sleeves. Thus the sealing sleeve 26 is formed 'with a series of circumferential corrugations 59 as may be seen in Fig. 2 and the sealing sleeve member 39 is provided with a slight bulge 60.

It will be readily appreciated that the described sealing construction also avoids the creation of any significant strain in the sealing sleeve that might arise from radial expansion and contraction of the shell 11. The sealing sleeve 26 fits around the shell 11 with sufficient clearance to avoid conflict with radial expansion of the shell relative to the face plate 12. The only effect that radial expansion of the shell can have on the sealing sleeve 26 is very slight flexure of the sealing sleeve and because of the extensive longitudinal dimension of the sealing sleeve, even the slight flexure will be extensively distributed.

While the described fabrication procedure is preferred, the procedure may be varied or other procedures may be used in practicing the invention. For example, the face plate 12 may be formed in. other ways and the annular face on the face plate to receive the end pressure of the shell 11, as well as the annular shoulder 58 to receive the radial pressure of theshell may be formed in the glass by a grinding operation.

Preferably the construction. shown in Figs. 1 and 2 is fabricated in such a manner as to result in normal compression contact between the rim of. the shell. 11 and the ring flange 38. that is backed by the glass shoulder 58.

Such. a result may be accomplished by properly relating the diameters of the shell 11 and the inner flange 38 of the sealing ring 25. Fig. 5 for example may represent the unrestrained diameter of the ring flange 38 and the unrestrained diameter of. the cylindrical part 16 of shell 11 at the normal. contemplated operating temperature of the finished cathode ray tube. By unrestrained diameter is meant the diameters of the shell and ring apart from each other prior to assembling.

Since the. thermal coefficient of linear expansion of the shell. 11 is greater than the thermal coefficient of linear expansion of the material of the ring flange 38, a rise. in temperature. of the. two members above the normal operating temperature will cause the shell, 11 to expand relative to the ring flange 38 so that the shell 11v may-telescope over the ring flange as shown in Fig. 2. Thus with the parts initially dimensioned as indicated in. Fig. 5, the preliminary heating of the shell 11 and the ring flange 38 in the above-described procedure for bonding. the face plate 12 to the ring 25 will expand thev shell 11 sufficiently to telescope over the ring flange 38'. After the glass bond is finished, the natural. cooling of the parts will tend to restore the shell 11 to its initial diameter and thereby cause the shell 11 to embrace the ring flange 38 and the glass shoulder 58 with a certain. desirable degree of tension. Thus at the normal temperature of the finished cathode ray tube the shell 11 will exert appreciable compression pressure against the ring flange 38 and glass shoulder 58.. As av result the parts will normally fit together tightly with consequent rigidity in the joint structure.

In the second form of. invention shown in 6 a one-piece sealing sleeve 63 of thin metal is employed which metal may either have substantially thev same coeflicient of thermal. expansion: as the faceplate 12 or. may be relatively thin,. soft. copper as. heretofore discussed. The sealing sleeve 63 is formed with an inwardly turned ffange 64 and a liberal loop or single corrugation 65 adjacent the flange. The flange 64 is bonded to the face plate 12 as shown to provide a flat annular face 66 for sliding contact by the rim of the shell 11. The major portion of the sealing sleeve 63 surrounds the shell 11 with a small amount of clearance as indicated in the drawing and the sealing sleeve is suitably bonded to the shell 11 at substantial distance from the face plate 12 in a suitable manner, for example by solder as shown at 67.

In the procedure for fabricating the construction shown in Fig. 6, first the sealing sleeve 63 is bonded to the face plate 12 by the application of heat to cause the periphery of the face plate to become plastic and flow to the configuration shown. It will be noted that the heated glass yields to permit entrance of the metal into the body of the glass to result in the formation of an annular shoulder 70 in the face plate lying against the inner surface of the shell 11. Preferably the dimension of the flange 66 of the sleeve 63 relative to the diameter of the rimof the shell 11 is such that the inner cylindrical surface of the shell is flush with the inner edge of the flange 64 at the temperature at which the cooling glass solidifies sufliciently to withstand compression engendered by further cooling of the shell member. Thus at the highest temperature in the operation of bonding the face plate 12 to the flange 64 of the sealing ring, the shell 11.will have a'larger diameter than shown in Fig. 6 but will cool and contract to the diameter of Fig. 6 at which temperature point the glass shoulder 70 solidifies to an unyielding extent. With further cooling the tendencyof the shell 11 to contract will result in appreciable tensioning of the rim of the shell around the glass shoulder 70 with consequent close fitting of the parts and with consequent rigidity in the joints.

In the form of invention shown in Fig. 7 a sealing sleeve 73 of the character heretofore described is formed with a flare orlip 74 at one end and at the other end is formed with an outwardly extending flange 75. Joined to the sealing sleeve 73 is a sealing ring 76 having an inwardly directed radial flange 77. A second sealing ring, 78 is mounted on the shell 11 and attached thereto by welding or solder as indicated at 79. This second ring 78 has an outwardly extending flange 80 positioned for bonding face to face to the flange 75 as heretofore described.v Preferably the sleeve 73 is formed with an offset 81 which serves substantially the same purpose as the loop 65 in the sleeve shown in Fig. 6.

In the fabrication sequence the ring 76 is united to the sleeve 73, the lip 74 and the flange 77 are bonded to the face plate 12 by the previously described application of heat, the ring 78 is sealed to the shell 11 while the shell 11 is isolated from the face plate 12, and, finally, after the face plate 12 is coated or an auxiliary screen inserted in the shell the parts are brought together and the two thin sheet metal flanges 75 and 80 are bonded together to complete the seal.

Preferably, the shell 11 is formed with an inwardly directed rim flange 84 as shown in the drawing to increase the area of the shell rim in sliding contact with the ring flange 77 and preferably the inner diameter of the rim flange 84 relative to the inner diameter of the ring flange 77 is such that the rim flange 84 in cooling contracts against the annular shoulder 85 formed in the face plate 12. In accord with this concept the rim flange 84 of the shell 11 is so dimensioned that it is approximately of the same inside diameter as the ring flange 77 when the glass of the face plate 12 is appreciably above the temperature at which the glass is solid enough for the shoulder 58 to act in compression to resist contraction of the rim flange 84.

An important advantage of the arrangement in Fig. 7, as preferably constructed is the selection of successive materials to provide a progressive series of thermal may have a coeflicient of approximately 9010- coefficients of linear expansion. Thus the steel shell 11 may have a coeflicient .of approximately 115.10- per degree centigrade in the range from room temperature to 500 C.; the coeflicient of ring 78 may be approximately 108.10 to 112.10; the coefficient of sealing sleeve 73 may be approximately 105.10 to 110.10 the coeflicient of the ring 76 may be approximately 90.10- to 95.10- and the glass for the face plate 12 Thus the coeflicient steps down at successive transition points with the resulting stresses divided among the transition points.

Fig. 8 shows the relative positions and dimensions of the parts while the glass is stillabove solidification temperature. The rim flange84 of the shell 11 coincides at its inner edge with the ring flange 77 but as cooling progresses, the rim flange of the shell contracts faster than the ring flange 77 so that the rim flange of the shell progressively intrudes into the body of the glass until the glass cools sufliciently to stop the contraction of the shell and thereby causes the parts to take the final relative positions shown in Fig. 7. Thus, the annular face of the face plate 12 with which the flange 84 of the shell qt makes sliding contact is'provided in part by the metal of the ring flange 77 and in part by the glass material of the face plate. Normally, there will be no substantial sliding action between the shell and the face plate because at normal temperatures the rim flange 84 of the shell will engage the glass shoulder 85 with substantial compression pressure and with expansion at higher temperatures such compression pressure will decrease but not disappear.

In carrying out the fabrication of the construction shown in Figs. 7 and 8, the shell 11 is separated from the face plate to permit the face plate to be coated or to permit the installation of an auxiliary screen. In the final assembly steps the shell 11 is preheated suificiently to permit the rim flange 84 of the shell to telescope over the glass shoulder 85, such preheating ordinarily being insuflicient to cause damage to the seal or to any auxiliary screen.

It will be apparent that the radially inward pressure against the thin metal sealing sleeve in the various forms of the invention will tend to collapse the sleeve, but the sleeve is usually reinforced against such pressure by being formed with at least one oflset loop or corrugation and in any event collapse will be prevented because the sealing sleeve is outside the periphery of the shell 11 and cannot collapse unless the shell collapses. The shell 11 in turn is reinforced by a circumferential shoulder in the face plate 12 such as the shoulder 58 in Fig. 2, shoulder 70 in Fig. 6, and shoulder in Fig. 7.

In the construction shown in Fig. 9, a sealing sleeve 88 of thin metal of the character heretofore indicated is formed with an outwardly turned flange 89 adapted to be joined face to face with a similar flange 90 of a ring 91. The ring 91 is similar to the previously described ring 78 of Fig. 7 and in like manner is welded or soldered to the shell 11 by solder or welding as indicated at 92. The sealing sleeve 88 is formed with an intermediate oflset 95 and at its outer end is formed with an inwardly directed radial flange 96 for sliding contact by the rim of the shell 11. The radial flange 96 in turn is formed with an inner cylindrical flange 97 which is reinforced in the man ner heretofore described by an annular shoulder 98 ot the face plate 12. The metal shell 11 is of the usual configuration but in this instance has a rim flange 99 provided by a ring 100 of angular cross section which is mounted on the inner circumference of the shell by suitable means such as rivets 101.

' The construction shown in Fig. 9 is fabricated in the manner heretofore explained and preferably provides normal compression contact between the rim flange 99 of the shell and the inner *flange 97 that is reinforced by 1 l the glass shoulder 98. It will be noted that the onepiece sealing sleeve 88 not only provides the surface for sliding contact by the rim flange 99 of the shell 11 but also provides the inner flange 97 that prevents the molten glass from encroaching on that surface.

Fig. 10 is illustrative of the fact that the invention may be embodied in a one-piece sealing sleeve of ex tremely simple construction. The sealing sleeve 105 is in the form of a straight cylinder with an outward flare or lip 106 to form a sealing bond with the outer circumferential edge of the face plate 12. When the face plate 12 is heated to form this bond with the sealing sleeve 105, the rim of the shell 11 is partially enveloped by the molten glass, thereby forming the usual annular should-2r 107 in the glass. As the shell 11 and the face plate 12 cool down after the bonding operation, the shell in con tracting faster than the glass forms the usual annular face 108 against which the shell is to be in sliding contact. The shell continues to contract as it cools until it is arrested by solidification of the glass at the shoulder 16?. The result as heretofore explained is normal. compressive contact on the part of the shell 11 with the annular glass shoulder 107.

The sealing sleeve 105 may be connected to the shell '11 in a sealing manner by solder as indicated at 110. If the sealing sleeve 105 is made of soft, thin, phosphorousfree copper, the copper will stretch so readily as to accommodate longitudinal expansion of the shell 11 without creating undue strain in the region of the bond between the lip 106 and the glass of the face plate 12. On the other hand, in the preferred construction, the sealing sleeve 105 is made of less yieldable material having substantially the same thermal coeflicient of linear expansion as the glass and the desired yielding action to prevent undue strain on the glass bond is provided by the solder 110. A solder suitable for this purpose may comprise 98% lead and 2% titanium. Such a solder composition is not only relatively soft to yield for the present purpose but also has the advantage of a relatively low melting point to minimize the necessity for excessively heating the shell 11. Silver solder is also yieldable for the present purpose. Thus the yielding action may be provided either by the metal of the sleeve itself or by the solder that bonds the sleeve to the shell 11 and such yielding action makes it unnecessary to form any offset loop or corrugation in the sleeve.

In the last form of the invention shown in Fig. 11, the shell 11 is formed with an outward radial shoulder 115 terminating in an outward cylindrical flange 116. An outer sealing sleeve 117 in the form of a straight cylindrical band is bonded to the cylindrical flange 116 by welding or solder as indicated at 118 and in turn is bonded to an inner sealing sleeve 120 by solder or welding as indicated at 121. Preferably the inner sealing sleeve 120 is deeply looped in cross-sectional configuration in the manner of a metal bellows, as shown, and at its inner end forms a radial face 123 and an inwardly turned rim flange 124, the rim flange 124 being reinforced by the usual annular shoulder 125 in the face plate 12. The radial shoulder 115 of the shell 11 is in sliding pressure contact with the radial face 123 of the inner sealing sleeve 120, and the shell 11 is in compression contact with the rim flange 124 of the inner sealing sleeve.

The construction shown in Fig. 11 is fabricated with the same basic sequence of operations heretofore discussed. The inner sealing sleeve 120 is bonded to the face plate 12, the outer sealing sleeve 117 is bonded to the shell 11, and, as the final fabrication step, the two sealing sleeves are bonded together by welding or solder shown at 121.

The various embodiments of the invention described in specific detail herein will suggest to those skilled in the art various changes, substitutions and other departures from my disclosure that properly lie within the spirit and scope of the present claims. For example, the glass face late .ma ;b h p y e S a'ped m s'pscla'l molds the final to said annular'face for sliding pressure contact by said figuration or may be ground to the final configuration required for the joint-construction.

I claim as my invention:

1. In an electronic vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope; a metal shell member forming an adjacent portion of the tube envelope, said shell member being separate from the glass member with discontinuity of bond therebetween but being in pressure contact therewith; and a flexible thin walled sealing sleeve means having one circumferential portion attached to said glass member and a second spaced circumferential portion attached to said shell member, the major portion of said sleeve means embracing said shell member for reinforcement by the shell member.

2. In an electronic vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope; a metal shell member forming an adjacent portion of the tube envelope, said shell member being separate from the glass member with discontinuity of bond therebetween but being in pressure contact therewith; and a flexible thin walled sealing sleeve means having one circumferential portion attached to said glass member and a second spaced circumferential portion attached to said shell'member, the major portion of said sleeve means lying outside said glass member and shell member, said flexible sleeve means being made of a plurality of circumferential members of different materials to provide at least one transition from one material to another in addition to the transition from the metal shell member to the flexible sleeve and the transition from the sleeve means to the glass member, said members having coefficients of linear thermal expansion varying progressively from a relatively high coefiicient for the shell member to a relatively low coefiicient for the glass member, with a portion of the total coeflicient dilferencc at each of said transitions to provide a relatively low coefficient differential at each juncture of two materials.

3. In a vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said face to exert pressure against the face in response to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member; and flexible circumferentialsealing means in the region of said annular face and rim having a first circumferential portion attached in a gas-tight manner to said glass; member and a second circumferential portion attached in a gas-tight manner to said shell, said two circumferential portions being spaced apart longitudinally of the envelope to permit the first circumferential portion to be heat-bonded to the glass member and then to permit the second circumferential portion to be heat-bonded to said shell without heating the first circumferential portion to a damaging temperature, said sealing means including a thin, flexible metal wall surrounding the metal shell, said thin wall having an inner diameter sufficiently larger than the outside diameter of the shell to provide clearance for thermal expansion and contraction of the shell.

4. In a vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said face to exert pressure against the face in response to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member; a sheet metal ring bonded rim; and flexible circumferential sealing means in the region of said annular face and rim having a first circumferential portion attached in a gas-tight manner to said glass member and a second circumferential portion attached in a gas-tight manner to said shell, said two circumferential portions being spaced apart longitudinally of the envelope to permit the first circumferential portion to be heat-bonded to the glass member and then to permit the second circumferential portion to be heatbonded to said shell without heating the first circumferential portion to a damaging temperature.

5. A combination as set forth in claim 4 in which said sheet metal is united with said sealing means.

6. A combination as set forth in claim 5 in which said sheet metal that is united with said sealing means is said first circumferential portion of the sealing means.

7. In a vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said face to exert pressure against the face in response to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member; and flexible circumferential sealing means in the region of said annular face and rim having a first circumferential portion attached in a gas-tight manner to said glass member and a second circumferential portion attached in a gas-tight manner to said shell, said second circumferential portion of said sealing means being separated from said first circumferential portion by a substantial width of material of the sealing means and in which the intervening portion of the sealing means is offset to flex in response to longitudinal expansion of the metal shell, said intervening portion being formed with circumferentialcorrugations to form a plurality of offsets.

8. In a vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said face to exert pressure against the face in response to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member; and flexible circumferential sealing means in the region of said annular face and rim having a first circumferential portion attached in a gastight manner to said glass member and a second circumferential portion attached in a gas-tight manner to said shell, said sealing means including a thin sheet metal sleeve that is outwardly looped in longitudinal cross-sectional configuration to provide a relatively long path for heat conduction between said two circumferential portions and to minimize the transmission of stress between the two portions.

9. In a vacuum tube of the character described, the combination of: a glass member forming one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said face to exert pressure against the face in re sponse to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member, said glass member being formed with an annular shoulder adjacent the inner circumference of said annular face to reinforce said rim against inward collapse; and flexible circumferential sealing means in the region of said annular face and rim having a first circumferential portion attached in a gas-tight manner to said glass memberv and a second circumferential portion attached in a gas-tight manner to said shell, said two circumferential portions being spaced apart longitudinally of the envelope to permit the first circumferential portion to be heat-bonded to the glass member and then to permit the second circumferential portion to be heat-bonded to said shell without heating the first circumferential portion to a damaging temperature.

10. A combination as set forth in claim 9 in which said rim normally embraces said shoulder in tension for compressive contact with the shoulder.

11. A combination as set forth in claim 10 in which a thin sheet metal facing is bonded to said face and to said shoulder for contact by said rim.

12. A combination as set forth in claim 11 in which said thin sheet metal facing is a unitary part of said sealing means.

13. A combination as set forth in claim 12 in which said thin sheet metal facing is said first circumferential portion of the sealing means.

14-. In a vacuum tube of the character described, the combination of: a glass member forcing one portion of the tube envelope, said glass member having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell reg istered with said face to exert pressure against the face in response to external atmospheric pressure, said rim of the shell being free for radial sliding action in response to thermal expansion and contraction of the shell relative to the glass member; and flexible circumferential sealing means comprising two thin metal sleeves attached in a gas-tight manner to said sleeve member and said shell, respectively, said two sleeves having outwardly extending flanges at their juncture, said flanges being bonded together face to face outwardly from their base portions to provide a joint that is yieldable to longitudinal stress thereby to prevent longitudinal stress in the sealing means suflicient to damage said glass member.

15. In a vacuum tube of the character described. the combination of: a glass face plate forming the screen portion of the tube envelope, said glass face plate having an annular face in a plane substantially perpendicular to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said annular face to CXCH pressure against the annular face in response to external atmospheric pressure, said rim of the shell being free to expand radially relative to the face plate in sliding contact with said annular face; and a flexible thin walled sealing sleeve having one circumferential member bonded to said glass face plate and a second circumferential member bonded to said shell so that said two circumferential members may be separately bonded to said face plate and said shell respectively prior to assembly of the face plate to the shell and then the two eircurnlcrential members may be bonded together to seal the juncture between the face plate and the shell.

16. A combination as set forth in claim 15 in which one of said circumferentialmembers is bonded to said annular face of the face plate for sliding contact by the rim of the metal shell.

17. A combination as set forth in claim 16 in which said one circumferential member is formed in cross-sectional configuration with an outward loop adjacent said annular surface of the face plate.

18. In a vacuum tube of the character described, the combination of: a glass face plate forming the screen portion of the tube envelope, said glass face plate hat ing an annular face in a plane substantially perpendicw lar to the axis of the envelope; a metal shell forming an adjacent portion of the tube envelope with the rim of the shell registered with said annular face to exert pressure against the annular face in response to external atmospheric pressure said rim of the shell being free to expand radially relative to' the face plate in sliding contact with said annular face, said face plate being formed with an annular shoulder located inside the rim of the shell to reinforce this shell against inward collapse; and a flexible thin walled sealing sleeve having one circumferential portion bonded to said glass face plate and a second peripheral portion bonded to said shell, said two circumferential portions being spaced apart to provide a relatively long path for heat conduction from the second circumferential portion to the first circumferential portion, said sealing sleeve being bonded both to the annular face and to the annular shoulder of the face plate for contact by the metal shell.

19. A combination as set forth in claim 18 in which said sealing sleeve comprises two members, one of which is bonded to the face plate at said annular face and annular shoulder and the other of which is bonded to said metal shell at a distance from the face plate to provide a relatively long path of heat flow by conduction from the region of bonding to the metal shell to the region of bonding to the face plate.

References Cited in the file of this patent UNITED STATES PATENTS 

